In facilities such as factories and warehouses, a self-propelled unmanned carrier is used, for example, to transport articles. Since such an unmanned carrier is not operated by any person, it has a mechanism for voluntarily detecting an obstruction on its route to avoid a collision with the obstruction.
For example, PTL 1 discloses an AGV (Automated Guided Vehicle) dolly provided with an obstruction detection sensor (obstruction detection device) including a light-emitting element and a light-receiving element. In the AGV dolly, when an obstruction exists at a predetermined distance from the obstruction detection sensor, the existence of the obstruction is detected by the obstruction detection sensor provided on a rotation shaft of wheels, and rotation of the rotation shaft by a driving device in the AGV dolly is stopped. Thus, detection of the obstruction is not delayed, the rotation can be immediately stopped, and a collision with the obstruction can be avoided.
PTL 2 discloses a bumper switch mounted on a bumper part of an unmanned carrier or the like to detect contact with an obstruction. In this bumper switch, side actuator plates are supported by their respective fulcrum members to be turned and displaced toward a switch element. For this reason, for example, when a side surface portion of the bumper switch comes into contact with an obstruction and pressure acts, the side actuator plates sensitively respond to the pressure, and are turned and displaced on the fulcrum members toward the switch element. Thus, the switch element is actuated, and the contact of the obstruction with the side surface portion can be detected accurately.
PTL 3 discloses a mobile device including an elastic member fixed to a side surface of a main body part having driving wheels, a bumper part that can be displaced in the horizontal direction by bending of the elastic member, a reflective photosensor that detects displacement of the bumper part in the horizontal direction in the body part, and a drive control part that detects a collision with an obstruction by analyzing a value detected by the reflective photosensor when the bumper part is displaced in the horizontal direction and controls a motor for driving the driving wheels so that the mobile device moves in a direction away from the obstruction.
As the obstruction detection sensor mounted in the AGV dolly described in PTL 1, for example, an LRF (Laser Range Finder) that detects an obstruction by scanning laser light frontward in the traveling direction is generally used to avoid a collision with then obstruction. In general, for the purpose of preventing a collision with an obstruction, the LRF is used to detect an obstruction existing on the route of the AGV by scanning laser light frontward in the traveling direction and to stop or decelerate the AGV, and is also used, for example, to detect the presence or absence of a free space in a warehouse or a storage space or to detect protrusion of an object. Thus, the LRF is a component that is highly important to traveling of the AGV.
The bumper switch described in PTL 2 is a component needed to reduce impact of contact when the unmanned carrier comes into contact with an obstruction or person suddenly appearing during traveling and to immediately stop the unmanned carrier upon detection of the contact.